The now classic treatment for stenotic lesions in the arterial system of the heart is either angioplasty followed with stent placement or simultaneous ballooning and stent expansion sometimes referred to as “direct stenting”. The stent is deployed and it acts as a scaffold to support and maintain the vessel in an “open” condition. This implant is typically expanded beyond the nominal diameter of the native artery to allow for the elastic recoil and proliferative smooth muscle response of the injured vessel wall. Although the usage of stents is widespread it is widely acknowledged that the restenosis rate for stented vessels is high for many categories of lesions.
Recently drug coated and drug eluting stents have been introduced to the marketplace and these combination devices promise to lower the rate of restenosis through the action of the drug and its impact on the healing response to the injury caused by the actions of angioplasty and stenting.
In addition to stent placement and angioplasty, local drug delivery has been proposed as a therapy. Typically such drug delivery is transmural or through the tissue of a vessel to an intravascular location within the wall itself. It has been presumed that the drug will remain at that targeted location longer and more effectively than a drug delivered to the target via the moving blood stream.
As of mid-2002, anti cancer agents and antibiotics have been delivered to coronary arteries via drug eluting stents. A multitude of agents such as Rapamycin analogs, Taxol/Taxan, Actinomycin D, antisense dexamethasone, Angiopeptin Batimistat, Translast, Halofuginon, nicotine, heparin, and ASA have been or are currently under consideration as deliverable from the surface or from within voids in a stent wall or stent coating.
Research has been conducted to determine dosage, dose delivery rate, drug action control, drug take up and time duration of delivery as parameters. Also the desirability of targeting of specific cell communities within the arterial wall has been explored. Treatment site selection and drug retention have been explored with reference to the endothelium, intima, media, adventia as well as vasa vasorum of the target vessel have been investigated.
This background reflects the current practice of “treating” stenotic lesions that severely impair blood flow through the vessel. The question remains of whether or not to treat vessels that are not hemodynamically significant but appear to have a lesion or vulnerable plaque at risk of rupture. When the interventional cardiologist's diagnosis shows which of these non-occlusive lesions are candidates for treatment conventional stenting may not be an optimal choice. However delivery of drugs or other non-drug treatments from a catheter based platform may be a desirable methodology. At present there is no effective interventionally based therapy for these “vulnerable” regions and lesions other than stenting.